Carrier telegraph receiver



Se t. 1

p 927 v. P. THORP CARRIER TELEGRAPH RECEIVER Filed Oct- 10. 1925 Sekcting batt Butt. 3122:.

INVENTOR V1? 1740170 BY j ATTORNEY Patented Sept. 20, 1927.

UNITED STATES PATENT OFFICE.

venom: r. rnonr, or arm area, New masax,assre1woa r urn-moan rm anon m ransom]; coxrnnga oonromrrox or NEW You rmenarn aacmvan.

j Application and amber 'io, ms. Serial no. arms. I

This invention relates to a receiving -'circuit arrangement for carrier telegraph systems, and more particularly to arrangements to reduce the effect of static interference 5 u n the received si al.

The effect of lightning and of other-disturbances of the character usually referred to as static interference upon a carrier telegraph receiving circuit has been found to produce 1 either of two effects, depending upon the condition of the circuit at the time the disturbance arises. When carrier current is being received from the distant end, and after being amplified is rectified to o erate the sensitive polar relay, thereby c osing the local loop, the effect of an interfering static impulse is to cause the polar relay to kick open. This is usually a short but violent kick. When no carrier current is bein re- 'ceived and the'relay armature is on its ck contact, an incomin static disturbance causes the relay to ki its armature to its closed ition. This is also a sharp, quick kick. accordance with the present invention, it is proposed to slow up the action of the receiving circuit so that it will not respond to an impulse of short duration such as is produced by static interference. This may be accom lished by reversing the polarity of the kic winding of the polar receiving relay. I

The invention may now be more fully understood from the following description when read in connection with the accom-- panying drawing, the figure of which shows a clrcuit diagram embodying a preferred form of the invention.

Referring to the drawing, the receiving circuit of a carrier telegraph system is shown comprisin the usual selecting circuit F connected on t e input side of an amplifier A, which may be of any well-known type, such, for example, as a vacuum tube. A rectifier tube It is provided, having the usual filament, grid and plate. The C battery is connected to the grid through a resistance 10, and a condenser 11 is provided to prevent the potential of the C battery from affecting the amplifier A. The potential applied to the grid through the resistance 10 is of such value that under normal conditions no space current can flow between the filament and plate dueto the B battery. A olar receiving relay PR having a mam win ing 11, a biasing winding 12 and kick winding 13 is provided. The main windin 11 is connected in circuit with the plate 0 the rectifier tube and the B battery. The biasing winding is connected in circuit with a hatte and serves to bias the armature of the re ay against its spacing contact S. The pull exerted by the biasing winding to hold the armature ainst the spacing contact S is in practice a out onehalf the pull exerted by the main winding 11 when carrier current is received to shift the armature to its marking contact.

The kick windin 13 is connected to the plate clrcuit throng a transformer comprismg a primary winding 1 and a secondary winding 2. The secondary winding 2 may be shunted by a variable resistance 1' for the purpose of reducin the kick in the winding 13 to a desired'va ue. A condenser 14 is bridged between the plate and the filament to Pass the high frequency component.

e arrangement above described is the same as the ordinary carrier telegraph recelving circuit as now employed in commercial practice, with the exception that the connections of the secondary winding of the transformer T are reversed with respect to the kick winding 13 of the receiving relay, and the resistance r is added. In the usual form of circuit, the winding 2 is so connected as to aid in'the movement of the armature under the influence of the operating current. It serves to quicken the action of the relay armature when moving from one contact to the other. In accordance with the resent invention, a. retarding action will produced upon the relay armature when an incoming signal is applied to the detector circuit. The relay will not operate until the detector current has reached approximately its maximum or steady state value. The same condition will exist when a telegraph signal is received. That is, when t e current starts to die down, an impulse will be produced in the seconda of the kick trans ormer and applied to the winding 13 in such a direction that it will tend to hold the relay on its contact until the operating current has approximately reached the zero value. I

It has been found that the time lag thus introduced into the operation of the relay eliminates the efiect of disturbances due to lightning and the like,which are enerally strong but quick im ulses of short uration. While the reason or this is not entirely clear, owing to incomplete knowledge of the character of lightning disturbances, the following tentative theory is .advanced for whatv it isworth, without vouching for, its accurac The efiectof a lightning disturbance is to roduce upon the transmission circuit a wave aving a very high potential and a sharp front. If this wave consists of more than one oscillation, it is so rapidly damped that I only the first pulse of the wave is of material consequence. This first pulse may be either positive or negative; and its elfect u on the Y receiving circuitwill depend upon t e con dition of the. circuit at the time. As has f already been explained, normally the grid of the rectifier tube isv biased sufliciently negative so that no current flows in the space circuit in the absence of the received carrier current. The effect of the rece1ved carr er current is to render the. II'd. less negative 1 thannormally during eac positive half of the received oscillations so that rectified pulses are produced in the output circuit. A

direct current component corresponding to the rectified pulsesjthus flows through the 7 operating winding 11 to shift and hold the e armature against its marking contact in opbeen momentarily interrupted durin position to the pull of the b asing winding. If at the moment a train of carrier waves is being received, a lightning disturbance should produce a sudden sharp wave, and

waves will not produce any rectified impulses in the output circuit. The result. will e as though the train of carrier waves had the sudden static disturbance, so that if t e action of the relay is very quick, (as is the case when the normal connection of the secondary winding 2 is employed), the armature of the relay will be shifted from its marking contact to its spacing contact during the static impulse. Where, however, the connections of the secondary 2 are reversed, as in the present invention, the effect of the static impulse to interrupt the rectified current and thereby cause the armature to be shifted is neutralized by the kick impulse which momentarily tends to hold the armature in its assumed position. Consequently, the static disturbance cannot cause a shifting. of the armature unless it is of long duration.

If the static impulse is of such a character that it arrives upon the grid of the rectifier tube with a positive potential at the time being receive at the time such a positive impulse was impressed upon the grid, a rectifiedrimpulse of current would flow in the output circuit. Consequently, if the relay were quick in its action, as is the case with the usual circuit arrangement, the armature which would be resting upon its spacing contact would be suddenly shifted to the marking contact, thus'mutilating the signal. If the connections of the secondary 2 are reversed, however, the sharp, sudden impulse of rectified current in the winding 11 W111 be opposed by the induced impulse in the winding 13 until the induced impulse dies down. Consequently,- the armature will not be shifted unless the disturbing impulse is of long duration. I

If the disturbing impulse arrives at the grid of the rectifier tube with a negative potential at a time when no carrier current is received, its only elfect is to make the grid more negative, and no current being at this time flowing in the winding 11, the increased negative potential of the grid merely tends to further prevent such flow of current. No disturbing efl'ect arises in this case. It .will be observed, then, that while either a positive or negative disturbance may mutilate the signal, the positive disturbance will only mutilate the signalif no carrier current is being received; and the negative impulse will only mutilate the signal when carrier current is being received. The efiect of the reverse of the connections of-the. winding 2 being to oppose the shifting of the armature fora brief interval after a chan e in current occurs, neither of these disturblng effects will have mutilated the signal unless the disturbance is unduly prolonged.

It has been found in practice that the arrangement herein described will operate uite satisfactorily during periods when lightning disturbances and other atmospheric discharges are quite prevalent. The circuit is, of course, slowed down to some extent by the use of this connection so that signaling must take place at a slightly slower rate. It is consequently desirable only to use a reverse connection of the winding 2 during periods when the disturbing influences prevail. During good weather conditions, the winding 2 should be so connected as to producea kick impulse in the winding 13 which from the spirit of the invention as defin in the following claims.

What is claimed is: e 1. A receiving circuit for a telegraph system comprising an operating circuit, a re ay from, said auxiliary winding and transformer being so (poled with respect to each other as to pro uce a force momentarily tending to prevent the shifting .of said armature.

5. In a carrier telegraph receiving circuit, a detector having an output circult, a receivingl relay havin an armature means norma y biasing-sai armature against one of its contacts, an operating winding in said havmg an armature, means to normally bias output circuit and an auxiliary windin said armature against a normal contact, an operating winding in said operating circuit for shifting said armature from its normal contact, and an auxiliary winding upon the same core as said operating winding and inductively associated with said operating circuit so as to receive a kick impulse therefrom, said auxiliary winding bemg so poled that the kick impulse momentarily opposes I the force tending to shift said armature.

2. A receiving circuit for a telegraph system comprising an operating circuit, a relay having an armature, a winding connecting in circuit with a local source to bias said armature against one contact, an operating winding in said operating circuit to shift said armature against the bias of said biasing winding, and an auxiliary winding u on the same core as said operating W111. ing and inductively related to said operating circuit so as to receive a kick impulse therefrom, said auxiliary winding being so poled that the kick impulse momentarily opposes the force tending to shift the armature in either direction.

3. A receiving circuit for a telegraphs stem comprising an operating circuit, a re ay having an armature, said armature being normally biased against one contact, an operating winding in said operating circuit to shift said armature to its alternate contact, and an auxiliary winding u on the same core as said operatin win mg and connected through a trans ormer to said operati ing circuit so as to receive a kick impulse therefrom, said auxiliary winding and transformer being so poled with respect to each other that the building up of a current or the cessation of the flow of current in said operating circuit will produce a momentary force in said auxiliary winding tending to oppose the shifting of said armature.

4. A receiving circuit for a telegraph systern comprising an operating circuit, a receiving relay having an armature, a biasing windin in circuit with a local source for normal y holding said armature against one of its contacts, an operating winding in said operating circuit for shifting said armature to its alternate contact, an auxiliary'winding upon the same core as said operating winding and a transformer for associating upon the same core as said operating win mg and inductively related to said output clrcuit' so as to receive a kick impulse therefrom, said auxiliary winding being so poled as to momentarily tend to oppose the shifting of (said armature in response to the building up or cessation of current in said operating winding.

6. In a carrier telegraph receiving circuit, a detector, an output circuit. for said detector, a receiving relay having an armature, a biasing winding connected in circuit with a local source to bias said armature against one of its contacts, an operating winding connecting said output clrcuit an respond:

ing to detected current therein to shift said armature to its alternate contact, and an auxiliary winding upon the same core as said operating winding and inductively related to said contact so as to receive a kick, I

impulse therefrom, said auxiliary winding being so poled as to momentarily tend to oppose the shifting of said armature in response to the building up or cessation of current in said operating winding.

7. In a carrier telegraph receivin circuit, a' detector, an output circuit there or, a receiving relay having an armature, means to bias said armature. against one of its contacts, an operatingwmdingfin said output circuitoperating in response to detected current to shift said armature to its alternate contact, an auxiliary winding upon the same core as said operating winding and a trans former for connecting said auxiliary winding to said output circuit so as to receive a kick impulse therefrom, said auxiliary winding and transformer being so poled with respect to each other as to produce a momentary force in said auxiliary winding, which tends to momentarily oppose the shifting of said armature in response to the building up or cessation of current in said operating winding.

8. A carrier telegraph. receiving circuit comprising a detector, an output circuit therefor, a receiving relay having an armamm, a biasing winding in circuit with a local source to produce a force tending to bias said armature against one of its contacts, an epfilrating wmdin in said output circuit ten g to shift sai armature to its alternate cont act in response to detected current, an euxlhary wmdmg upon the same core as sand operpbmg wmdmg and a transformer for assoclating said auxiliary wind- I name to this specifioation ifnhisflnh day of ing withsaid output cn'cuit so as to receive a kick impulse therefrom, said transformer and said auxlliary wmding bem so poled as to produce a orce momentar' y tending response/to the buildlng up or cessation of 0 current i1 1 said operating windlng. o

In testlmony whereof, I have signed'my October, 1925.

I VAUGHNZii. THoRP. 1* 

